This invention relates generally as indicated to a device for holding green tires during a pre-curing wait cycle.
In the manufacture of a tire, its various components, including reinforcing components embedded in a matrix of unvulcanized rubber or other unvulcanized rubberlike material, are assembled on a building form. The tire at this stage of the manufacturing process is commonly called a green tire. After being built, a green tire is transported to a shaping and vulcanizing press whereat it is shaped to its final form and vulcanized. There is almost always a waiting period between the production of the green tire and its subsequent curing. This time period can be referred to as the pre-curing wait cycle and can extend anywhere from a few hours to several days.
During the pre-curing wait cycle, a green tire is usually stored on a holding device. Of particular relevance to the present invention is a green tire holding device having a horizontal arm which extends through the opening of the green tire and engages an upper section of the inner periphery of the green tire. In other words, the green tire hangs from the horizontal arm. In this vertical position, the green tire has a tendency to sag or droop under its own weight, due to gravitational forces on the unsupported portions of the green tire, and become distorted. Specifically, the upper portion of the green tire which rests on the horizontal arm is constantly subjected to the gravitational pull of the lower portions of the green tire.
A need exists for a device that counters the constant gravitational forces for a green tire during the pre-curing wait cycle for that tire.
The present invention provides a green tire holding device comprising a frame and a turning spindle extending substantially horizontally from the frame. Preferably, the turning spindle turns at least one complete revolution. The turning spindle is shaped and sized to support a green tire and to turn the green tire so that no specific portion is subjected to the unsupported effect of gravitational force whereby distortion of the green tire during a pre-curing wait cycle is minimized. The device can include a plurality of turning spindles positioned to support the same green tire and/or different green tires. If a single spindle (per green tire) design is used, a convenient modification of current equipment is possible by attaching the turning spindle to the horizontal arm of an existing green tire holding device.
The turning spindle can continuously rotate the tire at a substantially constant speed of one revolution per hour or less. Alternatively, the turning spindle can rotate the green tire 180xc2x0 or less at spaced intervals. In either case, the turning spindle can be programmed for automatic turning operation thereby eliminating the need for any special training or procedures at the factory.
Thus, a method of manufacturing a tire according to the present invention comprises the steps of making a green tire, placing the green tire on a green tire holding device for a duration of a pre-curing wait cycle, and then curing the green tire. The green tire holding device has at least one turning spindle and the green tire is turned during the pre-curing wait cycle so that no specific portion of the green tire is subjected to the unsupported effect of gravitational force.